Removed dart error list view in favor of linter view.
Moved Fixit handling through linter (ALT-ENTER). For now all we pass to linter is a
'Quick Fix for ...' entry for each place it is available. When one is 'applied',
we use the analyzer to aync compute the actual list of possible fixes. I'll
make a change request to linter to allow passing in a Promise to create the
list of solutions, then we can get rid of the intermediate step.
Added passing of dart analyzer suggested correction to the linter.
Added Fixit icon to outline error list
Fixed some tooltips focus issue, by making Debouncer cancelleable.
fix https://github.com/dart-atom/dartlang/issues/1118